Lightning arrester



y 1942- J. SLEPIAN 2,290,254

LIGHTNING ARRESTER Filed June 13, 1959 WITNESSES: v INVENT OR I Josep/zSigma/2 I BY ATTORN Patented July 21, 1942 LIGHTNING ARRE STER JosephSlepian, Pittsburgh, Pa., assignor to Westinghouse Electric &Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsyl-Vania Application June 13, 1939, Serial No. 278,843

6 Claims.

My invention relates to electric discharge apparatus and has particularrelation to are extinguishing devices.

In circuit breaker apparatus for interrupting substantial current theprincipal problem which arises involves the prompt extinguishing of thearc ignited between the contacts when the breaker is opened. Inaccordance with the teachings of the prior art of which I am aware, achamber in which the arc may be extinguished is provided and the arc iseither ignited in the chamber or transferred to it. Since the range ofmovement of the contacts of a circuit breaker is in general relativelylimited, the expediency of striking the arc in the extinguishing chamberis only adopted where the conditions are such that they may be satisfiedby a relatively small chamber. Where the arc is transferred to theextinguishing chamber, the transfer takes place in discrete stagesthrough arc horns, or auxiliary contacts are opened in the chamber. Theresultant structure is relatively complex.

It is accordingly an object of my invention to provide an arcextinguishing device of simple structure for a circuit breaker.

Another object of my invention is to provide a lightning arrester thatshall respond to potentials of moderate magnitude and that shallfunction to efficiently interrupt the arc ignited.

A more general object of my invention is to provide an arc extinguishingarrangement of simple structure.

An ancillary object of my invention is to provide a contrivance forfacilitating the ignition of an arc in a desired region.

initiated over a silicon carbide surface disposed More concisely stated,it is an object of myinvention to provide an arrangement for localizingan arc in a region in which it may easily be extinguished or controlled.

My invention arises from the realization that a discharge may beinitiated over the surface of a semi-conductor such as silicon carbide,boron carbide, and zirconium compounds of the type used in the art forthe construction of resistance rods by the application of a relativelylow potential. Thus I have found that a discharge may be produced overthe surface of a rod of silicon carbide crystals, such as are sold underthe trade name of Carborundum crystals, by the application of apotential gradient of approximately 800 volts per inch. In other caseswhere the crystals were of different dimensions I have found 10,000volts to be required for a discharge. The magnitude of the potentialwhich produces the discharge is dependent on the dimensions andstructure of the surface. For example, a discharge may take place overthe surface of a single large silicon carbide crystal or a bar formed ofa number of crystals held together by a binder such as water glass or aceramic glaze.

. 6 This discharge takes the form of an are when it in an arcextinguishing chamber. A pair of fixed electrodes shunting the contactsis provided in the chamber and by reason of the ionization produced bythe discharge over the silicon carbide surface, an arc is ignitedbetween the electrodes. The are between the contacts is, therefore,interrupted and when the current next passes through zero the arc in thechamber is extinguished.

In accordance with another aspect of my invention silicon carbidesurfaces are provided along the surfaces of the slots of an insulatorwhich forms a gas in the presence of an arc. The surfaces facilitate theignition of an arc and, therefore, the arrangement responds to asubstantially lower potential than a corresponding arrangement in whichthey are absent.

The novel features I consider characteristic of my invention are setforth with particularity in the appended claims. The invention itself,however, both as to its organization and its method of operationtogether with additional objects and advantages thereof, will best beunderstood from the following description of a specific drawing in whichthe figure illustrated is a diagrammatic view showing the essentialelements of a circuit breaker constructed in accordance with myinvention.

The apparatus shown in the figure comprises a set of cooperative fixedand movable main contacts l l and 13, respectively, and a plurality ofsets of cooperative fixed and movable auxiliary contacts 15 and I1, andI9 and 2|. The sets of contacts II to 2| are interposed in seriesbetween a source 23 of any general type and a load 25, the main contactsH and I3 being connected between the auxiliary contacts I 5 to 2 I.

The movable contacts I3, l1 and 2! are mounted on insulating levers 27,29 and 3!, respectively, which are in turn secured to a pivotallysupport-ed pin 33. When the circuit interrupter is closed, thesupporting shaft is latched so that the contacts ll, l5 and I9 and I3,I! and 2|, respectively, are in engagement. To open the interrupter thelatch 35 is released by a solenoid 37 in the usual well known manner andthe pin 33 carries the movable contacts l3, l1 and 2| to the openposition under the action of a suitable spring 39. The are ignitedbetween the contacts when they are opened is interrupted within a hollowcylinder 4| of a material which forms a gas in the presence of an arc.In the preferred practice of my invention a cylinder ding the siliconcarbide near the outer region of the ceramic material when the rod ismolded.

At the ends of the rod '53, ring-shaped electrodes 65 and t! of asuitable conducting material are disposed. The electrodes are interposedbetween the source 23 and the load 25 in parallel with the contacts H to2!. The rod 43 is held in the insulating cylinder ll by a pair of rings4-5 and iii which are pressed into the cylinder and engage theelectrodes 45 and 41 at their ends. The supporting rings 49 and areperforated so that gas may flow through the cylinder G! with facility.The rod 43 is also provided with a pair of conducting terminals 53 and55 which are disposed adjacent to the electrodes 55 and M, respectively,and are rigidly secured to the rod. In the preferred practice of myinvention, the terminals should be mounted approximately from thecorresponding electrodes.

To produce the preliminary discharge over the silicon carbide surface,step-up transformers 51 and 59 are provided. The primaries 5! of thetransformers are connected across the auxiliary contacts l5 and H and i9and 2i. The electrode 45 and the associated terminal 53 are connectedacross the secondary 53 of one transformer 5'! and the other electrode4'! and its associated terminal 55 ,are connected across the othersecondary.

When the breaker is opened, the potential drop across the auxiliarycontacts l5 and I7 and E9 and 2| results in the impressing of apotential across the silicon carbide surface between the terminals 53and 55 and the electrodes 45 and Lil, respectively. The potential issufficient to produce a discharge over the adjacent surfaces. When thecontacts H to 2| are disengaged, the total potential across the contactsis also impressed between the electrodes 45 and 41. By reason of theionization produced by the discharge, the arc between the contacts II to2| is transformed into an are between the electrodes 45 and ll. Tofacilitate the transformation, a low resistance coil 65 is providedadjacent the main contacts H and I3. The coil is connected in serieswith the contacts II to 2| and carries the main arc current. By reasonof its magnetic field, the arc at the main contacts II and I3 is blownout and its transfer to the extinction chamber is facilitated. In theextinction chamber the heat of the arc causes the fiber cylinder fl toemit a deionizing gas and the arc is eX- tinguished when the currentpasses through zero at the end of the half-period following thetransfer.

In the modification shown in the figure, an insulator 43 surfaced withsilicon carbide is used. This structure may of course be modifiedwithout departing from the scope of my invention.

For example, the silicon carbide surface need not extend throughout thewhole length of the insulator 43. It may be restricted to the ends. In astructure which may be used with advantage in the practice of myinvention, an insulating tube is provided with silicon carbide ends. Thecomposite tube may be constructed by securing small cylindrical blocksof silicon carbide to the ends of a porcelain cylinder and fastening theterminals 53 and 55 and the electrodes 45 and 4'! to the siliconcarbide.

Although I have shown and described certain specific embodiments of myinvention, I am'fully aware that many modifications thereof arepossible. My invention, therefore, is'not to be restricted exceptinsofar as is necessitated by the prior art and by the spirit of theappended claims.

I claim as my invention: 1. In combination means for establishing anarc, an arc-extinguishing chamber on wall of which comprises a surfaceof the silicon carbide type, said means being outside said chamber,means for impressing a potential sufficient to produce a discharge oversaid surface, said means including means for connecting said arc inmultiple with said surface.

2. In combination an arc-extinguishing chamber having Walls which emit agaseous substance contact means, an arc-extinguishing chamber,

a surface of the silicon carbide type disposed in said chamber, meansfor connecting said contact means across said surface and meansresponsive to the opening of said contact means to produce a dischargeover said surface.

4; In combination a circuit interrupter having a plurality ,of pairs ofcontacts, an arc-extinguishing chamber, a crystalline surface of thesilicon carbide type disposed in said chamber,

means for connecting said contacts across said surface and meansresponsive to the opening of one of said pairs of contacts for producinga dischargeover said surface.

' 5. For use in the protection of a system including a load and a sourcefor supplying said load, the combination comprising a plurality of pairsof contacts interposed in series between said load and said source, anarc-extinguishing chamber, a crystalline surface of the silicon carbidetype disposed in said chamber, means for connectings'aid surface inparallel with said 'shunt'with said contact means and means for ignitingan are between said electrodes on the operation of said contact meansand igniting means including surfaces of silicon carbide withinsaid'chamber'and means for producing a discharge over said surface.

" JOSEPH SLEPIAN.

